Mouse Camera Movement is choppy/jittery

When I load up the game I get relatively steady 30-40 fps. FPS goes up when I keep the camera facing somewhat downward. When I look up at the town or sky, the camera movement becomes incredibly choppy/jittery. not smooth at all. But the fps only changes by about 2-4 frames per second. Any suggestions? I already tried turning all things good off lol. No change.